Products of converted lignocellulosic materials

ABSTRACT

A method of converting lignocellulosic materials into various useful products, the method being controlled to produce the different products in accordance with the demand for them in the market. All of the original lignocellulosic material is used in this method. An important product obtained from this method is lumber engineered and dimensioned in accordance with the demand, and having predetermined characteristics.

This is a continuation, of application Ser. No. 502,065 filed Aug. 30,1974 now abandoned which is in turn a division of application Ser. No.237,705 filed Mar. 24, 1972 now abandoned.

This invention relates to a method of converting lignocellulosicmaterials into useful products without waste, and products of thismethod.

In the past there has been a great deal of waste in the utilization oflignocellulosic materials, and particularly wood. During loggingoperations, the limbs of trees are cut off and are burned or left aroundto decay. In the mills a large percentage of the wood is lost insawdust, trimmings or cuttings, and the like. Some effort has been madeto reduce the amount of sawdust, and to convert the trimmings andcuttings into chips for use in manufacture of pulp. However, the wasteis still very great. In addition to this, many small trees are leftbehind in logging operations since it is uneconomical to cut and handlethem, and many species of trees and shrubs are not used at all sincethey are not considered to be suitable for the manufacture of lumber.

Many sources of lignocellulosic fiber are not commercially utilized forconstruction purposes because of inherent characteristics that make themeconomically unattractive, such as small diameter, low density, lowresistance to decay, poor grain properties, and poor strengthproperties. In many areas of countries such weed species can constitutea significant, if not the major, part of the available wood resource. InBritish Columbia, Canada, Western red cedar constitutes a significantpart of the coastal forest, something of the order of 22%. However, itsstrength properties and pulp yield characteristics are such as to makeit of little commercial value compared to such contiguous species asDouglas fir and hemlock. In some tropical areas, such as Malasia, thedesired species may occur at such a low frequency per acre as to allowfor only the most primitive segregation and cutting operations. In otherareas, the dominant vegetation consists of bushes, reeds, and otherwoody plants not suited for conventional conversion into constructionproducts. In addition to this non-utilization of non-processed woodfiber, is the very large amount of waste wood generated in the mosthighly automated, high yield log conversion systems. It is estimatedthat the waste wood amounts to about 45% of the total tree, taking intoaccount all low value uses of residues for fuel and soil conditioning.

The present invention contemplates the production of constructionmaterials, such as lumber, various types of panels, and the productionof pulp, from any source of lignaceous cellulosic fiber. The generalidea is to break down any lignocellulosic material into slivers, fibersor strands by any suitable means such as by slicing, crushing, shaving,peeling or the like. The aim in the breakdown is generally to produce aslong fibers as possible. During the breakdown there are produced smallor fine particles, medium length strands and long length strands. Thefine particles are utilized in the manufacture of pulp and/or fiberboards, the medium length are used in the manufacture of strand boards,chip boards and/or particle boards, and the long lengths aremanufactured into dimensioned lumber and/or board products. It is thisproduction of the dimensioned lumber that makes the process or methodpractical, since the lumber is engineered to give desiredcharacteristics, regardless of the type of the basic lignocellulosicmaterial. An important feature of this process is the fact that it canbe operated to produce the various products in accordance with themarket demand. If the demand for pulp is up and for the other productsis down, more of the material can be converted into short lengths orparticles. On the other hand, if the demand for strand boards, chipboards or particle boards is up, the percentage of medium lengths can beincreased at the expense of the long lengths. However, if the demand forlumber is up, as many long length are produced as possible. As thelumber products have the highest commercial value, it is usuallydesirable to aim to produce the highest possible amount of long lengthfibers.

The general advantages resulting from this process carry on into thedimensioned lumber field. The lumber can be produced in size andcharacteristics in accordance with the market demand. For example, ifthere is a relatively great demand for two by fours, a large percentageof the long fibers can be converted into these. On the other hand, ifother boards or timbers are particularly required, the production can beconcentrated on these.

This is a concept that can revolutionize the wood product producingindustry. Heretofore, the trees were converted into the best or highestpaying products possible. However, with the prior production methods,the control of the type of lumber produced is very limited so that if alarge number of, say, two by fours are in demand, the operation willalso result in the production of large number of boards or lumber ofdifferent sizes which may not be required at the moment. Thus, aproducer can end up with a large inventory of boards not needed at themoment when he tries to fulfill the sudden demand for boards or lumberof other dimensions.

The main product of this process is the dimensioned lumber. It ispossible to make any number of boards of the same or differentdimensions, and these can be given desired characteristics regardless ofthe original source of material. The term "board" as used herein isintended to include all kinds of boards, timbers and lumber of anydesired directions.

As stated above, the lignocellulosic materials can be broken down in anydesired manner. The fibers are separated by length into those fractionsmost suitable for the required end use, treated with such additives asmay be needed to give the required resistance to decay and fire, driedeither before or after the addition of adhesives, or they can be leftundried, and then combined with a binding material, and, possibly,combined with non-cellulosic fibers, such as glass, metals and plastics,and formed into a mass and either cast, molded, extruded or pressed intothe desired end product.

Any method of breaking up the raw lignacious cellulosic material intofibers will develop a wide range of fiber lengths and diameters. Themost profitable and useful end use is a lumber product suitable forconstruction purposes, followed by a strand panel board with strengthproperties similar to plywood, chip boards, and lastly the particleboard for essentially non-structural uses. A possible segregation of theparticles in the following lengths for the specified purposes is asfollows:

Dimensioned lumber; 6 inches to 4 feet

Strand board; 2 inches to 6 inches

Chip board; 1/2 inches to 2 inches

Particle board; Less than 1/2 inch

Pulp; Less than 1/2 inch

Any excess of any fraction can be broken down into lower lengths.

All of the products that can be produced by the present process,excepting the dimensioned lumber, are produced by known processes.

However, this invention contemplates the production of dimensionedlumber from any lignacious cellulosic material. Use of this concept willsignificantly affect the conventional forestry practices from thepresent emphasis upon merchantable lumber to that of a maximum yield ofwoody fiber per acre, and will result in a true tree farming approachutilizing fast growing, short cycle, high yield species rather than thepresent slow growing long cycle species.

As stated above, one of the advantages of the present process is theutilization of non-commercial "weak" species in the production of goodgrade lumber. Some species of wood, such as aspen and alder, areconsidered low value species and little used for commercial purposesbecause of their very low yield of merchantable lumber per/unit/acre oflogs. This low yield is due to the small size of log, the low strengthproperties, and the incidents of compression and tension wood causingwarping and twisting. Utilization of these species in the manufacture ofthe various products in accordance with this process makes very largevolumes of wood available for commercial use. A large percentage of thewaste from the standard logging sawmill and manufacturing procedures canbe converted to dimensioned lumber having more value than the use ofthese material for pulping. Smaller trees and shorter harvesting cyclescan be used in order to give an increase in wood yield from givenacreage.

The present process lends itself to the production of a uniform densitymaterial with guaranteed strength and durability properties, free fromthe inherent defects of normal lumber-knots, splits and densityvariations.

The strength properties of wood increase with increasing density. Allspecies for which data is at present available show this increase. Thisrelationship of strength properties to density is of major commercialsignificance in the use of lumber, resulting in allowable design stressvalues significantly below that of the average strength values of thespecies involved. Variations in the density of wood are due tovariations in its structure and the presence of extraneous constituents.The structure is characterized by the proportional amounts of differentcell types, such as fibers, tracheids, vessel ducts, and rays, and bytheir dimensions. Hereditary tendencies, physilogical and mechanicalfactors, position in the tree trunk, all affect the density of the wood.The relationships are very complex and not well understood. The resultis a wide variation in density within any one species which can be aslarge as a factor of 2 to 21/2. The dimensioned lumber of the presentinvention overcome these inherent variations in normal lumberproperties.

By choice of compressed density, resin solids and strand geometry,particular properties can be imparted to engineered or dimensionedlumber. A range of lumber-like products can thus be engineered to usespecifications, and these are competitive on an engineering basis withsolid lumber, metals, plastic and concrete.

If desired, fire retardants, preservatives, colorants and the like canbe added to the particles or strands used in the production of thedimensioned lumber.

The engineered or dimensioned lumber produced by this process is made upof cellulosic fibers or strands ranging from about 6 inches to about 4feet in length, and having a width of about 0.05 to 0.25, and athickness of about 0.05 to about 0.5 inch. These fibers are coated withadhesive in standard coating equipment, such as drum applicators orcurtain applicators. A water insoluble structural glue, such as phenolformaldehyde, is used to coat the fibers, although any suitable type ofglue can be used. The coated fibers are arranged in bundles and thensubjected in presses to pressures sufficient to produce a finishedproduct having predetermined dimensions and density. The pressures andtemperatures used are sufficient to produce the desired density. Forexample, pressures of from about 100 to about 400 psi have been found tobe suitable, and the fibers are subjected to a high enough temperaturefor a time sufficient to produce a temperature of at least 212° F.within the product. For example, a temperature of 300° F. for up to 30minutes has produced desirable products, but this time can be reduced.If high frequency energy is used for providing the heat, the pressingcan be done in around one minute.

Referring to the accompanying drawings,

FIG. 1 diagrammatically illustrates apparatus for carrying out themethod in accordance with this invention,

FIG. 2 illustrates one way of producing lignocellulosic material touseful fiber lengths,

FIG. 3 illustrates a piece of dimensioned lumber made in accordance withthis invention,

FIG. 4 is a graph comparing the modulas of elasticity to density inengineered lumber,

FIG. 5 is a graph illustrating the relationship of the resin solids usedrelative to the modulas of elasticity,

FIG. 6 is a graph illustrating the effect of strand of fiber length,

FIG. 7 diagrammatically illustrates the direction of springback of someforms of dimensioned lumber, and

FIGS. 8, 9 and 10 are graphs illustrating specified characteristics ofthe dimensioned lumber.

FIG. 1 diagrammatically illustrates apparatus for carrying out thepresent invention. The lignocellulosic material, such as logs, roots,branches, waste wood, shrubs and the like, are fed to a breakdown device10 where they are sliced, crushed or otherwise broken down into fibers.It is desirable to produce long strands or fibers for use in themanufacture of dimensioned lumber. For example, these can be from 6inches to 4 feet in length, 0.05 to 0.25 inch in width, and 0.1 to 0.5inch in thickness. In the general breakdown there will be fibers ofmedium length and very short fibers. The general aim is to produce asmany long fibers as possible since these are used in the production ofdimensioned lumber which is the most valuable product for the market. Itis at this point that the final output of the process can be controlled.The short fine fibers are used for pulping or fiber boards, while themedium length fibers are used in the manufacture of strand boards,chipboards, particle boards and the like. If the demand for pulp and/orthese different boards goes up relative to the demand for dimensionedlumber, more short fibers and/or medium fibers are produced at thebreakdown device 10.

The fibers suitable device 10 go to a separator 12 which separates outthe short length fibers to be used in the manufacture of fiber boards orpulp, or for any other purpose for which short length fibers aresuitable.

Some or all of the medium length and long length fibers may be directedto an applicator 14 where they are treated with fire proofing material,insecticides, preservatives, stains or the like before being sent on toa dryer 16. Some or all of these fibers can be by-passed directly todryer 16. The moisture content of the fibers is reduced to the desiredextent for the production of the final product. If desired, the mediumlength fibers may be separated from the long length fibers before theyreach dryer 16, in which case the different groups of fibers would beseparately dried in accordance with the demand.

In this example, the fibers from dryer 16 go to a separator 18 whichseparates them into the long fibers and the medium fibers. The longfibers go to a glue applicator 20 which may be in any desired form, suchas a drum applicator or a curtain applicator, and from here they go to apress or mold 22 which presses them under heat and pressure into lumberof desired dimensions and the desired density. There is another controlat this point, that is, the dimensions of the lumber produced is inaccordance with the demand. For example, if there is a great demand fortwo by fours, the percentage of these would be high relative to boardsof other dimensions for which the demand was not so great. Although thisdiagram merely shows one press or mold 22, it is obvious that therecould be several presses so that boards of different dimensions could bemade at the same time.

Separator 18 separates out the medium fibers from the long fibers, andthese are directed to a glue applicator 24, whence they travel to apress 26 which produces the type of boards required, such as strandboards, chipboards, particle boards, and the like. Here again, althoughone press only is shown, there may be several. In addition to this, the"press" is intended to mean any system necessary to produce the desiredparticle-type board.

What actually happens in this method or process is that the originalmaterial is broken down into fibers of different lengths, and then theseare reconstituted into dimensioned lumber, particle-type boards, pulpand the like. With this arrangement, there is no waste. In addition, theprocess is geared to handle all of the particles produced from theoriginal material, regardless of their length, and regardless of whetherthe lengths are accidentally or intentionally produced.

FIG. 2 illustrates one way of reducing lignocellulosic material, such asa log, to useful fiber lengths. A log 30 is cut by suitable slicingmaterial into slices 31, and then each slice 31 is cut into relativelythin pieces 32 which extend the length of slice 31. Each slice 32 has adesired width, such as 0.05 to 0.25 inch. Then each piece is cuttransversely into strands 33 of desired thicknesses, for example, 0.05to 0.5 inch. These preferably are the length of the pieces 32. It isobvious that during this slicing or cutting process, there will be a lotof fibers which are considerably shorter than the strands or fibers 33.As stated above, the medium length fibers can be used in the productionof particle-type boards, and the short fibers can be used in theproduction of pulp, or for other desired purposes.

FIG. 3 illustrates a piece of dimensioned lumber or board 38 made up ofstrands or fibers 33. These strands or fibers, after being coated with asuitable adhesive, are laid side by side and then pressed under heat andpressure into a board of desired dimensions, such as, for example, a twoby four. These strands can extend the full length of the board, asshown, or each strand may extend only part way through out the length ofthe board. The strands are laid side by side, but as these are of randomdimensions and lengths, they interlock to a degree so that there are notstraight glue lines extending from one surface to the other of theboard. The density of the finished product is determined by the amountof pressure and heat used in the press. This is another advantage ofthis method, that is, the boards produced can be not only of desireddimensions, but they can be made in desired densities in accordance withthe purpose for which they are designed. In addition, it is possible tosubject the long strands to a continuous pressing operation so thatboards of any desired length can be produced. As the strands areinterlaced to a certain degree, any length of board can be produced.

Although the lengths of the strands for different purposes can vary, thefollowing is an indication of pratical lengths for the differentpurposes:

Engineered lumber; 6 inches to 48 inches

Strand board; 2 inches to 6 inches

Chipboard; 1/2 inch to 2 inches

Particle board; Less than a 1/2 inch

Pulp chips and sawdust;

In the manufactured or dimensioned lumber, the resistance of theglueline to horizontal shearing forces is proportional to the length ofthe fiber to which the stress is being transmitted to the glueline. Itis also inversely proportional to the thickness of the glueline which isrelated to the fiber thickness to the extent that the degree to which a"closest packing" condition of the fibers is achieved. The optimum resincontent for any set of variables is that at which maximum strengthproperties are obtained, all else being equal. Theoretically, too littleresin gives insufficient coverage, and too much resin causes thickgluelines, thereby reducing strength. Variables affecting the optimumresin content are the fiber geometry and the pressure applied during thecuring of the resin.

The thing that makes this process an economical success is the fact thatengineered or dimensioned lumber can be made with equal strength to thatof top structural grade Douglas fir lumber. This can be either on anequal density basis using optimum fiber geometry and adhesive content,or it can be on an increased density basis using less favourable fibergeometry and adhesive content. The strength of the engineered lumber isessentially independent of the raw material species, but increased"springback" with moisture absorption occurs with the use of low densityspecies. The durability and stability are mainly controlled by adhesivecontent.

STRENGTH-DENSITY RELATIONSHIP FOR ENGINEERED LUMBER

FIG. 4 shows plots of the strengths (Modulus of Elasticity, MOE) againstcompressed density for engineered lumber made from 1/8 inch Douglas firstrands under the following conditions:

Strand length; 6 inches, 12 inches, 24 inches

Resin solids; 1, 3, 5% (Phenol formaldehyde solids to dry woodpercentage

Press pressures; 100 to 400 psi

These plots show that for any given conditions of strand length andresin solids the strenth of the engineered lumber increases withincreasing compressed density. The rates of increase, i.e. the slope ofthe strength with density are equal (the lines are parallel). Thislinear increase of strength with the density is characteristic of wood,i.e. if the clear wood strengths of the commercial western softwoods(USDA "Wood Handbook", p. 75-77) are plotted against ovendry density astraight line is obtained shown by the heavy straight line in FIG. 4.This line has the same slope as the engineered lumber lines and acts asan upper limit of those lines.

It will be seen that the 24 inches, 5% line is coincident with thelimiting wood strength line. It is believed that no engineered lumbercan be made with greater strength at a given density than this clearwood strength limiting line.

In FIG. 1 the MOE requirements of two grades of Douglas fir lumber,select structural and No. 3 structural are shown by horizontal lines(Standard Grading Rules No. 16, WCLIP, p. 135). This shows howengineered lumber can be made with equal strength to these grades forall conditions of strand length and resin solids which cross thehorizontal strength lines. For a given grade increased density isrequired to compensate for shorter strand lengths and reduced resinsolids.

STRENGTH VERSUS % RESIN SOLIDS

FIG. 5 shows that the optimum resin solids percentage is in the range3-5%. The plots at equal press pressure (and resulting density) leveloff in this range, any increment in resin solids giving only a marginalincrease in strength. This resin solids range is for 1/8 inch squarecross section strands. Increasing resin solids would be required forsmaller strand section because of increasing specific surface area inthe engineered lumber and vice versa with large strand cross sections.

EFFECT OF STRAND LENGTH ON STRENGTH

Lines taken from FIG. 4 are plotted in FIG. 6 to show the effect ofstrand length on strength at equal resin solids (5%). The 24 inch lineis almost coincident with the clear wood strength line, the 12 inch lineis about 20% below the clear wood strength line, and the 6 inch line isabout 50% below. The clear western softwood MOE density line can beassumed equivalent to engineered lumber with infinitely long strands.Thus the 24 inch strand lengths are the best approximation to infinitestrand lengths. The 24 inch length on an 1/8 inch square cross sectioncorresponds to a length to diameter ratio of 200:1 which has beenestablished as the optimum fiber geometry for glass fiber composites.(Motavkin, A. V., et al "Choice of Optimum Structure of Glass FiberBased Materials", Mekhanika Polimerov 5 (2): 288-297 (1969)).

THICKNESS SWELL OF ENGINEERED LUMBER AFTER MOISTURE ABSORPTION

The compression of the engineered lumber to any desired density has adisadvantage of "springback", the permanent residual thickness swellingwhich occurs on release of the compressive stress with moistureabsorption. This "springback" phenomenon is also experienced inparticleboard type products. In engineered lumber the thickness swellingand "springback" is dependent on the overcompression above theuncompressed density of the strand bundles (extrapolate the lines backto the density X-axis), the resin solids and the strand geometry. Thispermanent "springback" of about 5% for optimum strand length and resinsolids is not disadvantageous in lumber type applications of floorjoists and wall studs where the swelling would be restricted to thesmaller dimension direction as shown in FIG. 7.

EFFECT OF SPECIES ON THICKNESS SWELL AND "SPRINGBACK"

FIG. 10 shows the comparison of residual thickness swell in thecompressed direction ("springback") of aspen with that of Douglas firfor equal strand length and resin solids conditions. It will be seenfrom the FIG. that aspen has a greater "springback" than Douglas fir(about 7% more swell for all densities). This difference can beaccounted for if the two 5% 24 inch lines are extrapolated back to thedensity X-axis at 20 and 26 lb./cu. ft. for aspen and Douglas fir,respectively. The 6 lb./cu. ft. difference is approximately equal to thedifference clear wood dry densities (30.4-23.2=7.2) between Douglas firand aspen.

Thus the influence of species on swelling characteristics can bepredicted with reference to the Douglas fir data by comparison of clearwood dry densities and drawing lines parallel to the established Douglasfir standard swell line.

Engineered or dimensional lumber can be made with any desired strengthto above that of the structural grade of a high strength wood species,such as Douglas fir, by using wood fibers obtained from low quality logsand combining fiber length, resin content and final product density. Theexact combination of fiber length, resin solids and final presseddensity chosen will depend upon the economic and technical situationssuch as the fiber length in stock, the cost of the raw materials, andthe wood species available. Examples of such combinations to meetvarious grades are shown in the following Table:

                                      TABLE                                       __________________________________________________________________________                                      Resin                                                                             Density                                              MOE            Fiber Solids                                                                            Lbs/Cu/                                 Group                                                                             Grade    1,000,000                                                                          Species   Length In.                                                                          %   Ft.                                     __________________________________________________________________________    A   Douglas Fir                                                                   Structural                                                                    Select and #1                                                                          1.93           24    5   30                                                                  24    3   31.2                                                                24    1   35.5                                                      Douglas Fir                                                                             12    5   32.6                                                                12    3   35.6                                                                12    1   40.0                                                                6     5   36.0                                                      Aspen     24    5   35                                                                  24    5   31                                                        W. Red Cedar                                                                            12    5   32                                          Douglas Fir                                                                   Structural #2                                                                          1.74           24    5   270                                                                 24    3   29                                                                  24    1   34.5                                                                12    5   30.5                                                                12    3   32.7                                                      Douglas Fir                                                                             12    1   37.5                                                                6     5   34.2                                                                6     3   37                                                        Aspen     24    5   31.5                                        Douglas Fir             24    5   31.5                                        Structural #3 and                                                                           W. Red Cedar                                                    Light Framing           12    5   30.5                                        Construction                                                                           1.54           24    5   25.0                                        Standard and            24    3   27                                          Utility                 24    1   31.5                                                      Douglas Fir                                                                             12    5   28                                                                  12    3   30.5                                                                6     5   34                                                                  6     3   34.5                                                                6     1   40                                                        Aspen     24    5   28.5                                                                24    5   28                                                        W. Red Cedar                                                                            12    5   23.5                                    B   Pacific Hemlock                                                                        1.30           24    5   23                                          Structural #3 and       24    3   25                                          Light Framing           24    1   29                                          Construction            12    5   26                                          Standard and  Douglas Fir                                                                             12    3   28                                          Utility                 12    1   33.5                                                                6     5   31                                                                  6     3   32.5                                                                6     1   38                                                        Aspen     24    5   25                                                                  24    5   23.5                                                      W. Red Cedar                                                                            12    5   25.5                                    __________________________________________________________________________

As can be seen, the strength of the engineered lumber can be independentof the raw material species so that weak species, such as Aspen andWestern Red Cedar, can be used in the manufacture of the higheststrength lumber grades, even though their natural occurring densities of23.7 and 20.6 lbs/cu. ft., respectively, would normally relegate them tothe lowest strength grade of 1.000 MM psi MOE. The actual volume of dryfiber required per MFBM of engineered lumber will depend upon therequired grade, the density of the wood species, the required density ofthe engineered lumber for that species, and the length of the fibers. Inpractice, it is possible to mix species and fiber lengths in variousproportions to make the most effective use of the available rawmaterial.

I claim:
 1. A discrete dimensioned structural lumber product comprisingadhesively bonded, substantially straight wood strands having lengths ofat least 12 inches, average widths of 0.05 inch to 0.25 inch and averagethickness of 0.05 inch to 0.5 inch, said strands being disposed, side byside lengthwise of the lumber product in substantially parallelrelationship with adhesive bonding adjacent strands, .Iadd.but withsubstantially no straight glue lines extending from one surface to theother of the product, .Iaddend.the total amount of adhesive .Iadd.resin.Iaddend.solids in said lumber product being from 1% to 5% by weight,said lumber product having a modulus of elasticity for a given dry wooddensity within the boundaries in FIG. 4 of the curve of western softwoodclear lumber as an upper limit of modulus of elasticity for a given drywood density and as a lower limit of modulus of elasticity for a givendry wood density the curve for 24 inch .[.fiber.]. .Iadd.strand.Iaddend.length 1% resin solids.
 2. A discrete dimensioned structurallumber product according to claim 1 wherein said lumber product has amodulus of elasticity of at least 1.30×10⁶ p.s.i. and a dry wood densityof not more than 40 lbs. per cubic foot.
 3. A discrete dimensionedstructural lumber product according to claim 1 wherein said lumberproduct has a modulus of elasticity within the range of 1.17 to 2.2×10⁶p.s.i.
 4. A discrete dimensioned structural lumber product consisting ofadhesively bonded, substantially straight wood strands having lengths ofat least 12 inches, average widths of 0.05 inch to 0.25 inch, andaverage thickness of 0.05 inch to 0.5 inch, said strands being disposed,side by side lengthwise of the lumber product in substantially parallelrelationship with adhesive bonding adjacent strands, .Iadd.but withsubstantially no straight glue lines extending from one surface to theother of the product, .Iaddend.the total amount of adhesive .Iadd.resin.Iaddend.solids in said lumber product being from 1% to 5% by weight,said lumber product having a modulus of elasticity for a given dry wooddensity within the boundaries in FIG. 4 of the curve for westernsoftwood clear lumber as an upper limit of modulus of elasticity for agiven dry wood density and as a lower limit of modulus of elasticity fora given dry wood density the curve for 24 inch .[.fiber.]. .Iadd.strand.Iaddend.length 1% resin solids.
 5. A discrete dimensioned lumberproduct according to claim 4 wherein the strands are at least 1/8 inchthick and at least 1/8 inch wide.
 6. A discrete dimensioned lumberproduct according to claim 4 wherein the dry wood density of the lumberproduct is from 23 to 40 pounds per cubic foot.
 7. A discretedimensioned lumber product according to claim 4 wherein the length ofthe strands is at least 24 inches. .Iadd.
 8. A discrete dimensionedlumber product according to claim 1 wherein the strands are at least 1/8inch thick and at least 1/8 inch wide. .Iaddend..Iadd.
 9. A discretedimensioned lumber product according to claim 1 wherein the dry wooddensity of the lumber product is from 23 to 40 pounds per cubic foot..Iaddend..Iadd.
 10. A discrete dimensioned lumber product according toclaim 1 wherein the length of the strands is at least 24 inches..Iaddend..Iadd.
 11. A discrete dimensioned structural lumber productconsisting essentially of adhesively bonded, substantially straight woodstrands having lengths of at least 12 inches, average widths of 0.05inch to 0.25 inch, and average thickness of 0.05 inch to 0.5 inch, saidstrands being disposed, side by side lengthwise of the lumber product insubstantially parallel relationship with adhesive bonding adjacentstrands, but with substantially no straight glue lines extending fromone surface to the other of the product, the total amount of adhesiveresin solids in said lumber product being from 1% to 5% by weight, saidlumber product having a modulus of elasticity for a given dry wooddensity within the boundaries in FIG. 4 of the curve of western softwoodclear lumber as an upper limit of modulus of elasticity for a given drywood density and as a lower limit of modulus of elasticity for a givendry wood density the curve for 24 inch strand length 1% resin solids..Iaddend..Iadd.
 12. A discrete dimensioned lumber product according toclaim 11 wherein the strands are at least 1/8 inch thick and at least150 inch wide. .Iaddend..Iadd.
 13. A discrete dimensioned lumber productaccording to claim 11 wherein the dry wood density of the lumber productis from 23 to 40 pounds per cubic foot. .Iaddend. .Iadd.
 14. A discretedimensioned lumber product according to claim 11 wherein the length ofthe strands is at least 24 inches. .Iaddend.